Idiopathic pulmonary fibrosis is a chronic, fatal lung disorder grouped with the fibrotic lung diseases. Studies with these patients have correlated physiologic parameters with histopathology; quantitated gas exchange abnormalities; characterized content and rates of synthesis of collagen in lung biopsies; demonstrated elevated inflammatory cells and immunoglobulin-G in broncho-alveolar lavage fluid, developed methods to quantitate the uptake of 67 Gallium-citrate in lung as a non-invasive measure of lung inflammation; and shown that peripheral blood lymphocytes from these patients recognize collagen as antigenic and produce lymphokines when exposed to it in vitro. Evaluation of drug therapy of this disease with corticosteroids and immunosuppressive agents is still ongoing.